Get flash to fully experience Pearltrees
Alpine glaciers have long been recognized as sensitive indicators of climate: just as glaciers often shrink due to melting in summer and grow by accumulating new snow in winter, changes in their size over longer periods indicate a warming or cooling climate. Annual measurements of a glacier’s thickness or length are used to tell if accumulation of snow or loss of ice has dominated over the year. The difference in accumulation and loss is called a glacier’s mass balance. When melting exceeds snow accumulation, a glacier loses mass.
In the Arctic Ocean, the area covered by sea ice grows and shrinks over the course of the year. The total area covered by ice usually reaches its maximum extent in early March. Once spring arrives with more sunlight and higher temperatures, the ice begins to melt, shrinking to its minimum extent each September. The 2011 summer minimum sea ice extent was 4.3 million square kilometers: the second smallest (following 2007) of the satellite era. The image above depicts sea ice extent on September 9, 2011, the date of minimum extent for the year.
A variety of gases contribute to Earth’s natural greenhouse effect, including methane, carbon dioxide, and water vapor. In addition to helping regulate the Earth’s surface temperature, water vapor is also a key stage of the water cycle, ferrying water and heat through the atmosphere from one place on Earth to another. On an everyday level, the amount of water vapor in the air—the humidity—influences how hot and sticky the air feels and how hard an air conditioner has to work for us to feel cool.
With its large heat capacity and tremendous volume, the global ocean has vastly more potential to store heat than the atmosphere or the land surfaces. The top two meters of ocean water contain about as much heat as the entire column of atmosphere above them. The ocean’s tremendous ability to store and release heat over long periods of time gives the ocean a central role in stabilizing Earth’s climate system. The colors on the map above show how much heat the top 2,300 feet (700 meters) of the ocean contained in 2011 compared to the average from 1955 to 2006. Orange and blue areas show where the upper ocean’s heat storage rose or fell compared to its average value by as much as 4 gigajoules per square meter — that’s enough energy in one square meter alone to power a 100-watt light bulb continuously for nearly a year. An arrowhead-shaped swath of blue extends out from the equator in the eastern Pacific, reflecting La Niña conditions that persisted throughout most of the year.
La Niña conditions in the tropical Pacific Ocean throughout much of 2011 contributed to an overall cooler year than 2010, which ranked as either warmest or second warmest year on record, depending on a range of analyses. The map above shows 2011 surface temperatures across the globe compared to the long-term average. Places that were up to 7 degrees Fahrenheit cooler than the 1981-2010 average are dark blue, near-average temperatures are white, and places where temperatures were up to 7 degrees F warmer than average are red. Warmer-than-usual temperatures dominated both land and sea. La Niña contributed to the cooler than average sea surface temperatures in the equatorial Pacific as well as cooler temperatures in southeastern Asia, northwestern United States, and parts of Australia where La Niña drove more precipitation. Unusually high temperatures affected most land areas during 2011, with the most prominent warmth across the higher latitudes of the Northern Hemisphere.
Although the troposphere and the stratosphere—the first two layers of the Earth’s atmosphere starting from the surface—share a boundary, they don’t have a lot in common, starting with their temperature profiles. From the surface to the top of the troposphere at an average altitude of about 10 kilometers, temperatures get colder the higher you go. In the stratosphere, which extends from about 10 kilometers to 50 kilometers, it’s the complete opposite: temperatures get warmer the higher you go. The two layers also have different kinds and amounts of gases, including water vapor, and different circulation patterns. They react differently to things like La Nina (which cools the surface and the troposphere, but warms the stratosphere) and volcanic eruptions (which cool the troposphere, but warm the stratosphere).
The oceans are Earth’s biggest storage bin for heat. While heat is stored and mixed throughout the depth of the ocean over decades to centuries, it is the temperature at the surface that plays a significant role in seasonal and yearly variation in climate. Sea surface temperature also has a major impact on ocean life, including coral reef health, and populations of phytoplankton, which are the base of the whole ocean food web. The map above shows sea surface temperature during 2011, compared to the long-term average from 1981 to 2010. Places that were up to 9 degrees Fahrenheit colder than the 1981-2010 average are dark blue, near-average temperatures are white, and places where temperatures were up to 9 degrees F warmer than average are red.
The average temperature for the contiguous United States during June was 2°F above the twentieth-century average. Scorching temperatures during the second half of the month broke or tied over 170 all-time temperature records in cities across America. June temperatures also contributed to a record-warm first half of the year and the warmest 12-month period the nation has experienced since recordkeeping began in 1895. The map above shows where in the United States June 2012 temperatures were different from the 1981–2010 average.
Ned Gardiner, Climate Visualization Project Manager, NOAA Climate Program Office. The 2012 Hurricane Season is off to an early start. Here we can see Tropical Storm Aletta spinning up off the coast of Mexico. It was followed by Alberto off the coast of South Carolina. And although these were mild storms, this is the first time in recorded history there were tropical storms in both the Pacific and Atlantic basins before June first. Let’s take a closer look at the climate conditions driving the 2012 Hurricane Outlook.
The average global temperature (land and ocean) for May 2012 was the second warmest May temperature since recordkeeping began in 1880, and the temperature over land surfaces was the warmest on record for May. May 2012 also marks the 327th consecutive month with a global temperature above the 20th-century average. The last month with below average temperatures was February 1985.
The average temperature for the United States during May was more than 3°F above the long-term average, making it the second warmest May on record. The month’s high temperatures also contributed to the warmest spring, warmest year-to-date, and warmest 12-month period the nation has ever experienced since recordkeeping began in 1895. The maps above show where May 2012 (top) and year-to-date (bottom) temperatures were different from the 1981-2010 average across the contiguous United States. Shades of red indicate above-average temperatures and shades of blue indicate below-average temperatures—the darker the color, the more unusual the temperature difference.
Deke Arndt, Chief of the Climate Monitoring Branch, National Climatic Data Center. The entire United States, from the Rockies east, was warmer than normal for the first five months of 2012. And everywhere you see red on this map, temperatures have been above normal.
Narwhals breathing in a lead at the surface. Photo by Glenn Williams, courtesy of Wikimedia Commons . The Twin Otter plane that carries Kristin Laidre two hundred kilometers off the west coast of Greenland has Plexiglass bubble windows installed on both sides of the cabin. When Laidre peers through the glass, she can see the blank expanses of ice and snow covering the ocean’s surface in all directions, including directly beneath her. That’s where Laidre, a marine mammal biologist at the University of Washington’s Polar Science Center , has trained her eyes to look—down at the cracks of open water that blemish the otherwise pristine fields of ice. It’s often tedious work, playing “I spy a narwhal,” but when she catches sight of the whale, it makes the waiting worthwhile.
In the dim light of early spring in the Arctic, a high-resolution digital camera on a NASA research plane shot the photo below while flying over the Arctic Ocean. The photo documents what polar scientists mean when they describe the “thinning blanket” of sea ice across the Arctic Ocean. Compared to older, thicker ice (left), the young, thin ice (right) is more transparent, with numerous cracks and openings.
Jake Crouch, Climate Monitoring Branch of the National Climatic Data Center Since the beginning of 2012, drought conditions have worsened along the eastern seaboard, adding to a dry picture for much of the United States. One way to think about drought is by how much rain falls over a long period of time. This map shows the difference from the expected amount of rain that fell in the continental United States from January through April.